There is a fixing device of an image forming apparatus which heats a heat roller using plural heaters with different light distribution peaks. In such a fixing device, temperature detectors arranged at the light distribution peak positions of the respective heaters detect the temperature of the heat roller and the temperature of the heat roller is thus controlled. Also, conventionally, anomaly of each heater is detected on the basis of the result of temperature detection acquired at the time of temperature control of the heat roller during printing. JP-A-2002-184554 is known as disclosing a technique of detecting anomaly of plural heaters.
However, in a fixing device which has an auxiliary heater to heat a heat roller over its whole length in addition to plural heaters with different light distribution peaks, anomaly of the auxiliary heater cannot be detected using the result of temperature detection acquired at the time of temperature control of the heater roller. Therefore, there is a risk that a delay in noticing the anomaly of the auxiliary heater may impair the proper fixing capability of the fixing device.
Thus, it is demanded that a fixing device which detects anomaly of a heater to enable early detection of anomaly of an auxiliary heater, maintenance of proper fixing capability of the fixing device and hence enhancement of productivity of an image forming apparatus should be developed.